linux-kernel - Re: [PATCH 3/3] rust: dma: add as_slice/write functions for CoherentAllocation

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Message-ID: <4a48338e-64a1-4740-ae1f-7458507a009e@gmail.com>
Date: Thu, 10 Apr 2025 12:02:37 +0300
From: Abdiel Janulgue <abdiel.janulgue@...il.com>
To: Alexandre Courbot <acourbot@...dia.com>, a.hindborg@...nel.org,
 ojeda@...nel.org
Cc: Danilo Krummrich <dakr@...nel.org>,
 Daniel Almeida <daniel.almeida@...labora.com>,
 Robin Murphy <robin.murphy@....com>, Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <benno.lossin@...ton.me>, Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>,
 "open list:DMA MAPPING HELPERS DEVICE DRIVER API [RUST]"
 <rust-for-linux@...r.kernel.org>, Marek Szyprowski
 <m.szyprowski@...sung.com>,
 "open list:DMA MAPPING HELPERS" <iommu@...ts.linux.dev>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] rust: dma: add as_slice/write functions for
 CoherentAllocation

Hi Alex,

On 08/04/2025 06:08, Alexandre Courbot wrote:
>> +        }
>> +        // SAFETY:
>> +        // - The pointer is valid due to type invariant on `CoherentAllocation`
>> +        // and we've just checked that the range and index is within bounds.
>> +        // - `offset` can't overflow since it is smaller than `self.count` and we've checked
>> +        // that `self.count` won't overflow early in the constructor.
>> +        unsafe {
>> +            core::ptr::copy_nonoverlapping(src.as_ptr(), self.cpu_addr.add(offset), src.len())
>> +        };
> 
> How about leveraging as_slice_mut() so this unsafe block can be removed?

as_slice_mut is still unsafe, no? So we couldn't remove unsafe block still?

Thanks,
Abdiel